Facebook debugger alternative: test your link previews instantly
Facebook's official Sharing Debugger is slow, rate-limited, and requires a Facebook developer account. This free alternative replicates exactly what facebookexternalhit does: a real HTTP request with Facebook's user-agent, revealing the raw HTML and Open Graph tags Facebook reads when someone shares your link.
The same crawler powers link previews across Facebook, Messenger, and Instagram - together over three billion monthly users. If your og:title, og:description, or og:image tags are injected client-side by a JavaScript framework, Facebook sees nothing and your shared links look broken.
Paste a URL below to see what Facebook actually receives from your page.
How to use this tool
- 1
Enter the URL you plan to share. Facebook's crawler is preselected on this page.
- 2
Click 'Simulate crawl' to fetch the page as facebookexternalhit.
- 3
Review the 'Social preview card' to see the title, description and image as they would appear in a post or a Messenger chat.
- 4
Check 'Open Graph tags detected' for og:title, og:description, og:image and og:url. Any that are missing from the list are missing from the HTML Facebook receives.
- 5
Once the tags are in place, run the URL through Meta's Sharing Debugger and choose 'Scrape Again' so Facebook replaces the preview it has already stored.
How it works
The test sends a request with the header 'facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php)', reads the HTML that comes back and extracts every Open Graph property from it. The preview card on this page is drawn only from those tags, so it shows what Facebook can build, not what your page looks like in a browser.
Facebook fetches a link the first time it is shared and then reuses the stored result. That is why fixing your tags does not change old previews: the stored copy has to be refreshed, either by scraping the URL again in the Sharing Debugger or when Facebook next revisits the page on its own schedule.
Three things break previews even when the tags exist. The og:image URL must be absolute and publicly reachable, because the crawler fetches the image in a separate request. The image should be at least 200 by 200 pixels, with 1200 by 630 recommended for a large card. And the page must not redirect the crawler to a login or consent screen, because Facebook reads the tags from wherever it ends up.
Understanding Facebook (facebookexternalhit)
When someone shares a link on Facebook, Messenger, or Instagram, Facebook's crawler (facebookexternalhit) fetches your page to generate a link preview card. This card shows a title, description, and image pulled from your Open Graph (OG) meta tags in the raw HTML.
Facebook's crawler does not execute JavaScript. If your OG tags are injected client-side by React, Vue, or another framework, Facebook sees an empty page and generates either a generic preview with no image or no preview at all. This dramatically reduces engagement on shared links.
The impact of broken link previews extends beyond Facebook. Links shared in Messenger (which has over a billion users) and Instagram link stickers also use the same crawler. A missing or broken preview means fewer clicks, less engagement, and lower reach for your shared content.
Pre-rendering ensures that Facebook's crawler receives fully-formed HTML with all OG tags present, resulting in rich, visually appealing link previews that drive engagement and clicks.
Frequently asked questions
Why does my Facebook link preview show no image?▾
Facebook's crawler reads OG tags from raw HTML only. If your og:image tag is injected by JavaScript after page load, Facebook cannot see it. Use this tool to check whether your OG tags are present in the raw HTML response.
How do I force Facebook to refresh my link preview?▾
Use Facebook's Sharing Debugger tool (developers.facebook.com/tools/debug) to scrape your URL again. If your OG tags are still missing from the raw HTML, the preview will remain broken until you fix the underlying issue with pre-rendering or server-side rendering.
Does fixing Facebook previews also fix Instagram?▾
Yes. Instagram, Facebook, and Messenger all use the same crawler (facebookexternalhit) to generate link previews. Fixing your OG tags for Facebook automatically fixes them for all Meta platforms.
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